Creating Serverless projects fail to find Fleet Server URL

[mrodm]

While creating Elastic stacks using the serverless provider, sometimes the elastic-package stack up command fails to find the Fleet Server URL. This can be observed specially in the CI daily jobs. For instance:

• https://buildkite.com/elastic/integrations-serverless/builds/1398#01993633-373e-46ed-804b-348b49476655/425-454
• https://buildkite.com/elastic/elastic-package-test-serverless/builds/548#01993725-bd96-4312-aca7-f7bc1d972eaa
• https://buildkite.com/elastic/elastic-package-test-serverless/builds/546#01992cd8-eb64-4fca-8aa8-c841c1f0e045

This could be solved at least in these two different ways:

• Adding retries to the CI commands: [CI] Add retry to test serverless pipeline #2894
• Adding retries in the elastic-package code: [Serverless] Add retries to get default Fleet Server URL #2901

[mrodm]

I think adding retries to get Fleet Server URL in code (#2901) would be a better approach than adding retries to the CI scripts (#2894).